1. Field
Aspects of the present invention relate to rolling mills producing hot rolled products at either high or low delivery speeds, and more particularly to an improved trim shear for trimming the front and tail ends of the entire speed range of such products.
2. Description of Related Art
As herein employed, and by way of example only and without limitation, the term “high speed” means speeds higher than about 80 m/sec, and the term “low speed” means speeds lower than about 79 m/sec. Typically, and again without limitation, products having diameters ranging from between about 4.0-9.9 mm are produced at high speeds, and products having diameters ranging from between about 10.0-25.0 mm are produced at low speeds.
Conventional high speed trim shears typically employ one set of trim knives to trim the front and tail ends of the entire range of products exiting from the mill at either high or low speeds, and one set of chopping knives to chop the trimmed front and tail ends into shorter scrap lengths. A pivotal switch delivers the products to the trim knives, and a single three channel delivery guide directs the trimmed front and tail ends to the chopping knives while allowing the main length of the product to continue on for further downstream processing and/or handling.
The use of one set of trim knives and one delivery guide has been seen to significantly compromise shear performance when handling high speed products. Of necessity, the spacing between the shear knives and the size of and spacing between the delivery guide's entry bell mouths and guide troughs must be large enough to accommodate the larger low speed products. The wide spacing between the shear knives requires the switch to pivot through large angles, which can be problematic when delivering the relatively limber high speed products. Also, the enlarged entry bell mouths and guide troughs do not provide adequate support and guidance for the smaller high speed products.